Undercover policeman Jim Boyling married an activist and allegedly told her about other undercover operatives. Photograph: Guardian

Environmental campaigners had been invited to the meeting at the Cock Tavern pub in Euston in June 1999. They were members of Reclaim the Streets, a group that had days earlier brought the City of London to a standstill. By chance, two strangers sat next to each other: Jim Sutton, an articulate, if at times moody, 34-year-old fitness fanatic who relished his role as the group's driver, a function that earned him the sobriquet "Jim the Van"; and Laura, 28, an idealistic activist. Laura (not her real name) did not know that this new acquaintance, a man she would go on to marry and have children with, was in fact Jim Boyling, a police officer living undercover among eco-activists.

Laura has told her story to the Guardian in the hope that it will serve as a warning to police chiefs that their surveillance operation "wrecks lives".

Her account of how she came to know and love someone who turned out to be a police spy – which is substantiated by official documentation and has not been denied by police – will almost certainly lend weight to calls for a public inquiry, chaired by a judge, into the surveillance of protesters.

"I was reading stories that this was happening to so many other women who were at risk of falling for their lies," says Laura, who was divorced from Boyling two years ago. "Having got through what I got through with my children I felt I had knowledge that could help other people and that I needed to do that."

She adds: "The impression in the press was that this was an isolated incident, that it was a really 'unusual thing' – but this is not true. I know of multiple cases. We're talking about a repeated pattern of long-term relationships and, for me at least, the deepest love I thought I'd ever known."

Her story suggests the collateral damage from a decade-long operation to infiltrate the protest movement is wider than police chiefs had expected. She says the deception that predated their marriage in 2005, with profound consequences for her wellbeing and that of their children, made her feel "like a prostitute; just an unknowing and unpaid one".

Already, three separate inquiries have been launched following the controversy surrounding Mark Kennedy, a Metropolitan police officer who spent seven years working undercover before turning against his seniors.

In its ongoing investigation into the surveillance operation, the Guardian has identified two other police officers who lived for years in the protest movement.

Boyling, a serving Met officer at the SO15, the force's counter-terrorism unit, is the fourth. His ex-wife alleges he encouraged her to change her name by deed poll in an unsuccessful attempt to conceal their relationship from senior officers.

Until recently, she says, she was still devastated by what had happened. "I'd been suffering post traumatic stress for a long time," she says. "I wasn't even able to recognise my face in the mirror."

When Laura met the man she assumed was a fellow activist, Boyling had already spent around four years in the protest movement.

Pulling the strings

Andrew James Boyling had adopted the alias "Jim Sutton" around 1995, and initially joined hunt saboteur groups and, according to friends, took part in anti-GM crop protests in Ireland and a "food summit" in Rome in 1996.

According to Laura, who says she had lengthy discussions with Boyling about his deployment during their nine-year relationship – once he had come clean to her, at least – the purpose of his police work was to infiltrate the closed ranks of those figures pulling the strings of Reclaim the Streets.

An environmental group counting anarchists and anti-capitalists among its ranks, Reclaim the Streets was a colourful collective opposed to cars. During its protests, members would block roads and start impromptu street parties. One notorious technique involved either crashing or parking "sacrificial cars" in the middle of traffic, sealing off the road. For police, they clearly constituted a potentially dangerous group of anarchists whose demonstrations had a record of descending into disorder.

Boyling's operation would prove to be so successful that he played a central organising role behind the so-called Carnival Against Capitalism in 1999, one of the major anti-capitalist demonstrations of the past two decades. Those involved in organising the protest recall that he was "navigator" in a car that had been intended to block Upper Thames Street, in central London, kickstarting a day in which thousands of activists would clash with police.

The woman who was driving the car – purchased for £200 – recalls how Boyling made what at the time appeared to be a stupid error. He left the window open, enabling police to open the door, take off the handbrake, and push the car away.

Confronted over his error, Boyling was said to have replied: "Oh, I forgot." The protest went ahead anyway, but it was a setback for the activists.

It seems that Boyling's deployment started around the time of the birth of the National Public Order Intelligence Unit, which took over the running of police agents embedded in the protest movement in 1999.

Three years later, having returned to uniformed duties, Boyling would receive a letter of commendation from an assistant commissioner at the Met.

The signed certificate noted his "outstanding devotion to duty and determination over an extended period in the investigation of serious crimes".

It was four months after the Carnival Against Capitalism, in June 1999, after a night in another pub, that Laura says she began to have a meaningful relationship with Boyling. "For the most part while he was undercover we had a blissfully in-love relationship," she says. "In the beginning I nearly broke it off because it almost felt too strong; he was a perfect blueprint for something I didn't even know I was looking for."

By February 2000, Laura says, the pair moved into a flat in East Dulwich, which they adorned with Celtic and African patterned throws. Laura says she became aware Boyling was "under-developed ideologically". "The thing about Jim is that he never really says much. He seemed to be bright but there seemed to be holes in his political development," she says.

"He didn't seem to like putting himself out there and making an effort, which is weird for someone who works in community-based groups."

Jim the Van was also known as "Grumpy Jim", and Laura says her boyfriend also raised eyebrows by a seeming reluctance to get involved in a sustainable activist culture, once refusing to help pick up rubbish at a campsite. "He was interested in disrupting, not building, it surprised me but I put down to immaturity." Despite a slight sense that he did not fit in, Laura never suspected her boyfriend was a police informant – except for on one occasion.

"It's such a cliche – but it was the way he was cleaning his walking boots," she said. "I suddenly thought, 'Who is this intruder?' – and then I came to and suddenly he was Jim again. It was such a brief moment and it made such little sense that I blanked it."

But despite their loving relationship, Laura says Boyling's moods grew increasingly erratic until, in September 2000, he said he was leaving for Turkey, from where he planned to hitchhike to South Africa. He then vanished.

'He no longer existed'

Confused, Laura says she spent more than a year trying to track him down. She tried to locate his family members – people who, it transpired, did not exist – and then travelled to South Africa. "He no longer existed in physical presence or on paper," she says. "I didn't know what to think or what to do."

Tipped off that Boyling had returned to England and was living in Kingston, Surrey, Laura moved there hoping to find him, she says. But it was a chance encounter, in the bookshop where she was working, that saw them reunited.

"He said: 'Don't be angry,' and I said I wasn't," she says. "He asked for a hug and he smelt the same, which was weird. We went for a coffee by Kingston Bridge and he said: "This can't be, I'm a police officer." At the time she was "very vulnerable", she says, as she had used "all my savings trying to find him, and I was very thin, down to 6 stone 12lb".

She said he refused to leave the police. "He said they would hound him. And I said that if he believed in leaving them, we could run away together and live a normal life anywhere in the world. He agreed."

Two weeks later, Laura says, she was pregnant. What ensued were, according to Laura, several painful and difficult years in which the pair maintained a relationship while living apart. They would eventually have two children.

"He said he would tell the police what he could get away with and nothing else. He promised me he was no longer working undercover and that there were no more agents in her movement because police had lost interest."

But Laura said she came to have reason to believe her husband was not being honest. He appeared determined that no one should know about their relationship.

She said he encouraged her to change her name by deed poll, saying that if she did not, there was a danger their address would be discovered and their child – then unborn – put at risk.

The Guardian has seen the deed certificate that confirms the change in name, and lists Boyling, who gave the occupation "police officer", as a witness.

Laura now believes that Boyling was desperate to hide their relationship from police, and alleges he gave false information to his seniors about their marriage to conceal her activist past.

She also says he encouraged her to cut ties with the activist community and wanted to "train" her in the art of deception. "He said the trick was to have a whole and detailed story but not tell too much of it," she says.

Boyling, however, may have struggled to balance his two lives.

"He said he missed that [activist] life – he said it was great because it was like being God. He knew everyone's secrets on both sides and got to decide what to tell who and decide upon people's fate."

According to Laura, the classified information Boyling said he had access to included wiretaps of one of her friends in the protest movement and "details of the private lives of activists", including, she said, information about what was contained in their luggage after they were stopped at passport control.

"Initially he promised me that he was the last officer in my movement and he was pulled out because the police no longer had any interests or concerns there, but that was a lie," she says.

"I found this out when he insisted we hide on our first visit to Kingston Green Fair [a sustainability event], because he had seen another undercover agent who knew us both and that this man would take it straight back to his superior."

After their two children were born, the couple married under Laura's new name in 2005. But it was not until two years later, in 2007, that Laura recalls two of Boyling's police colleagues visiting their home.

Laura said her then husband told her that he had only recently told one of the men about their relationship. The other, his long-time boss, had only known since 2005. She was told that both officers, to whom she was introduced by name, had worked as undercover agents.

Boyling later named one other supposed activist as a undercover police officer, and gave identifying descriptions of several others, according to Laura. If true, the suggestion that, as well as marrying an activist, Boyling had identified fellow undercover operatives could prove highly damaging for police chiefs, who say the actions of Kennedy are a rare example of "Stockholm syndrome".

Warning to others

Laura and Boyling's marriage was officially brought to an end around two years ago, when the pair divorced. Looking back, she believes their relationship should cause serious alarm. Senior police officers tasked with managing the fallout from the Kennedy controversy maintain that sexual relationships with activists are strictly prohibited, and rarely occur. However out of the four undercover police officers identified by the Guardian, three, all men, stand accused of having sex with activists. Two, Kennedy and Boyling, are known to have maintained long-term, meaningful relationships lasting several years.

"Jim complained one day that his superiors said there was to be no more sexual relations with activists anymore – the implicit suggestion was that they were fully aware of this before and that it hadn't been restricted in the past," Laura says.

"He was scoffing at it saying that it was impossible not to expect people to have sexual relations. He said people going in had 'needs' and I felt really insulted. He also claimed it was a necessary tool in maintaining cover."

Despite fearing the consequences of speaking out, Laura said she hoped her story would be a warning.

"Everybody knows there are people in the movement who aren't who they say they are. Being too paranoid would hinder everything. But you don't expect the one person you trust most in the world not to exist. It wrecks lives. You don't expect it, especially when you really are not important. I don't think the Met consider us at all … I find it shocking that so much public money is being spent on that to put members of the public under surveillance."

Boyling and the Met have been asked to respond to all the allegations about his undercover deployment and subsequent marriage to Laura, but neither has offered comment.